A method of making axonometric projection drawings from orthographic projection drawings is described in "Graphics for Engineers" written by R. P. Hoelscher et al. and published by John Wiley & Sons, Inc. This method involves the troublesome procedure of arranging separate front view and plan view on a drawing board in a specified relationship relative to each other. "Seizu no Rekishi (History of Drawing)," written by Peter J. Booker (translated by Masatoshi Hara) and published by Misuzu Shobo of Japan describes a method of making a specific axonometric projection drawing from an orthographic projection drawing as drafted. However, these references mention nothing about the making of desired axonometric projection drawings and rulers for making such drawings.
I contrived a novel method of making desired axonometric projection drawings from orthographic projection drawings and provided a drawing instrument for use in drafting such drawings on which U.S. Pat. No. 3,867,762 has been granted. With reference to FIG. 1, the method will be described below of making an axonometric projection drawing from a plan view and a front view of a cube drafted by orthographic projection.
A vertical line UV of an orthographic projection drawing is inclined clockwise through an angle .phi. with respect to a vertical line N.sub.1 N.sub.2. The intersection of the lines UV and N.sub.1 N.sub.2 is indicated at O.sub.1. The angle .phi. will be referred to as the inclination angle of orthographic projection drawing. The line UV may be inclined counterclockwise with respect to the line N.sub.1 N.sub.2, in which case an axonometric projection drawing of the cube will be obtained as it is seen from above on the left-hand side. Parallel lines La, Lc, Le, . . . sloping downward at an angle .alpha. with respect to a horizontal line are drawn through the corner points of a front view PLV of the orthographic projection drawing which is placed as inclined at the angle .phi.. Upwardly extending lines Ma, Mb, Mc, . . . are then drawn through the corner points of a plan view PLH at an angle of .beta., i.e. 90.degree.-.theta. with respect to a horizontal line to provide intersections Ta, Tb, Tc, . . . on a horizontal line T.sub.1 T.sub.2. Lines Na, Nb, Nc, . . . are drawn from the intersections Ta, Tb, Tc, . . . at an angle with respect to perpendiculars to the line T.sub.1 T.sub.2, the angle being equal to an angle .theta. between the perpendiculars and the lines Ma, Mb, Mc, . . . Lines connecting the intersections a, b, c, . . . of the lines La and Na, lines La and Nb, lines Lc and Nc provide an axonometric projection drawing. In this method of drawing, ad, ab, ae will be termed main projection axes, and the angle 2.theta. an inversion angle.
As will be described later, the values of the angles .alpha., .beta., .phi. and 2.theta. are determined in accordance with the kind of the axonometric projection drawing desired. The lines Ma, Mb, Mc, . . . can be regarded as the light beams emitted from the points of the plan view PLH and reflected by the horizontal line T.sub.1 T.sub.2 as indicated at Na, Nb, Nc, . . . Accordingly, this projection method will be termed "the plan view emitter method." Like the plan view emitter method, the front view emitter method is feasible. Although axonometric projection drawings have heretofore been made from orthographic projection plan view and front view, they can be made also from orthographic projection front view and side view. In this case, the drawings can be made also by the front view emitter method and side view emitter method. FIG. 2 shows a case in which an axonometric projection drawing is made from orthographic projection front view and side view by the front view emitter method.
This invention discloses rulers for use in making axonometric projection drawings by the emitter method.